I. Field of the Invention
The present invention relates to the field of batteries, and more specifically, to a battery pack controller for lithium-ion battery packs that provides power to portable electronic devices.
II. Related Art
Battery packs are a critical component of portable electronic devices, such as cellular telephones, laptop computers, and compact disc (CD) players, and similar types of battery-operated devices. The longer a battery pack can provide power to a cell phone or laptop the longer a user is able to enjoy use of those items. Moreover, the shorter the time it takes to charge a battery pack, the sooner the user is able to use those items away from a power outlet.
Conventional battery packs include a number of features to make the battery pack last longer and safer to use. For example, conventional Lithium-ion battery packs include a protection circuit, which is generally in the form of an integrated circuit (IC), that disconnects the battery within the pack from the battery-operated device when over voltage, under voltage, over current, and short circuit conditions exist. Without such protection circuitry, the battery pack could become damaged and catch fire causing personal injury and/or property damage. In addition to having a protection circuit or IC, some conventional battery packs include a separate data monitor IC. A data monitor IC is an IC that monitors various characteristics of the battery within the battery pack. For example, a typical data monitor IC will monitor the total current flowing out of the battery. By monitoring the current flowing out of the battery, the data monitor IC can be used for "gas gauging" the battery. Gas gauging refers to determining the amount of "life" remaining in a battery, that is, the amount of usable charge left in the battery. This feature enables users to know roughly how much time they have left to use the electronic device to which the battery is providing power.
A drawback of providing the protection and data monitoring features is that providing these features increases the cost of the battery pack because two separate ICs are added to the design.
Another drawback of conventional battery packs is that they require an external charger to provide current regulation when charging the batteries within the battery pack. An external charger adds to the cost, weight, and bulkiness of portable electronic devices.
Yet another disadvantage of conventional battery pack systems is that they require an external charger to provide a carefully regulated direct current (DC) voltage to charge the batteries within the pack. Such carefully regulated chargers are much more expensive than simple unregulated chargers.
What is, therefore, desired is a system to reduce the cost of a battery pack without having to sacrifice features such as battery protection and data monitoring. What is further desired is a battery pack system that does not need a charger with tight voltage and current regulation requirements to charge the batteries within the battery pack.